A variety of locks, deadbolts, chains and latches have been used as forms of security for preventing unwelcome access through a door. Unfortunately, due to their respective shapes and configuration with respect to a door frame, many of these are prone to failure under surprisingly little force.
For example, door chains and bar locks mounted on an outer side of a door frame and slideably engageable with mountings attached on a face of the door itself are ubiquitous and commonly available in the marketplace to provide additional security for private homes, offices, and hotels alike. However, because such locks are secured with screws and bolts placed parallel to the initial direction of an openly swinging door, force applied to the door may easily cause the screws and bolts to fail, pulling the mount itself free from the door and/or door jamb. Sufficient force may even cause the chain or bar to break or come unsecured from its mount.
As another example, deadbolts are commonly attached along an inner edge of a door to engage with the door jamb in a position perpendicular to the initial direction of an openly swinging door. Although the bolts themselves are sturdy enough to withstand high forces, they are known to physically tear through doors and doorframes. This not only allows a hinged door to admit possible intruders, but also damages the door and door frame in the process. Deadbolts even have an additional disadvantage of being susceptible to lock picking from the outside.
Attempts have been made to solve these problems. U.S. Pat. No. 4,575,140 to Dargis, for instance, discloses a door fastener that operates by connecting a strike plate in a door jamb to a plate slotted for positioning over a door handle. U.S. Pat. No. 6,641,185 to Hale et al. discloses a strike plate having two apertures for receiving arm portions of a U-Bar that partially encircles a shank portion of a door knob. Although each of these solutions avoid some of the shortcomings of the aforementioned locks, they require the door to remain completely closed while the lock is in use. This may prevent individuals protected by the locked door from securely screening visitors before deciding whether or not to permit entry.
Although various proposals have been made to solve the problem, none of those in existence combine the characteristics of the present invention. Therefore, there is a need for a lock that can be readily incorporated into the existing structure of the door jamb independent of a need to modify it. Moreover, there is a further need for a lock that optionally maintains the door in a completely closed position or prevents the door from being fully opened to admit potential intruders or unwanted guests.